1. Field of the Invention
The invention relates to the formation of plasticized proteinaceous materials and compositions containing the same especially for the preparation of chewing gums and confectionery compositions. The plasticized proteinaceous materials have properties that enable them to replace one or more conventional ingredients in chewing gums and confectionery compositions to provide products which are edible and/or biodegradable.
The plasticized proteinaceous material is made by first combining at least one protein and at least one plasticizer which have been matched according to desirable criteria. The solid state combination is then treated under heat and controlled shear conditions to produce a plasticized proteinaceous material having unique properties, that is especially suitable for gums and confectionery compositions.
2. Description of the Prior Art
Proteins are polypeptide chains of amino acids having molecular weights of from about 5,000 up to and including several million. All proteins are constructed from the same set of twenty amino acids. The side-chains of these amino acids differ in size, shape, charge, hydrogen-bonding capacity and chemical reactivity. Thus, different proteins may exhibit different chemical and physical properties.
Although many proteins may have similar amino acid compositions, the sequence of amino acids is unique to each protein. The polypeptide chains of proteins can be folded in specific ways, depending on their amino acid sequences. The structure of the proteins themselves is determined and maintained by interactions between the different amino acids that form the polypeptide. The specific linear sequence of amino acid residues that determines the native biologically active structure is influenced by environmental conditions. The diversity in protein structures and functions signifies that the relative importance of intrinsic properties in polypeptides and proteins depend upon each of the individual proteins.
The chemical and physical forces, both covalent and noncovalent that generally determine the structure and specific conformations adopted by proteins include covalent bonds, hydrogen bonds, electrostatic interactions, hydrophobic interactions and weak, nonspecific attractive and repulsive forces.
Proteins are held in their respective conformations by a number of different interactions, such as hydrophobic interactions, hydrogen bonding, ion-pair interactions, metal ion coordinations, and van der Waals interactions. The cross linking of various portions of proteins by the formation of disulfide bonds between pairs of amino acid residues can also impact the conformations of proteins.
The three dimensional structure adopted by proteins in solution is a result of all of the above-mentioned interactions. The structure may also be changed by altering the temperature or the solution conditions. Heat, pH and changes in solvent conditions can lead to conformational changes which cause proteins to denature and lose their native structures. The denaturation of proteins is typically irreversible. Naturally, these changes lead to changes in the properties of proteins, which may be either beneficial or detrimental to the formation of a product.
Denaturation is the most unique property of proteins since no other natural polymer can be denatured. Denaturation is defined herein as "any modification of the secondary, tertiary or quaternary structure of a protein molecule, that does not break covalent bonds". A change in the protein structure is usually associated with some changes in at least one of the physical, chemical or functional properties of the protein. The denaturation of proteins is often thought of as a two-state process, so that proteins are either in the state of native conformation or in the state of denaturation. It is now clear, however, that this is an oversimplification, since there are believed to be several additional intermediate states that proteins assume.
The degree of change in the structure of proteins and thus in their properties, depends on the nature of the individual protein itself, as well as on the type and extent of denaturation. Very little is known about the intermediate states of protein structure. It is possible that the intermediate states may have different degrees of reactivity compared to the fully denatured protein. However, it is clear that proteins may react in three ways upon denaturation: (a) no alteration in molecular weight despite change in shape, (b) dissociation into sub-units of definite uniform size, and (c) aggregation.
A typical denaturation may occur without alteration in molecular weight and it is not always certain that dissociation or depolarization of a protein is accompanied by denaturation. Aggregation of proteins, however, most commonly occurs as a result of heating and may be averted by the presence of denaturants. The process of aggregation is difficult to control and is sensitive to environmental factors such as pH, ionic strength and solvent composition, and also depends on the time and rate of heating but does not give a linear time-dosage response. Aggregation therefore is a secondary phenomenon dependent on the electrokinetic potential of the denatured protein molecules.
The nature of proteins in the state of aggregation may be the most important property of proteins in terms of their functionality. The forces that govern the interactions between protein molecules to allow the formation of aggregates is believed to be the same as those forces that act to create the secondary and tertiary structures of the individual molecules.
The degree of change in structure and thus the properties of proteins depend in part on the manner in which proteins are denatured. Among the most important changes in proteins as a result of denaturation are: (1) decrease in solubility, (2) loss of biological activity, (3) increase in reactivity of constituents groups, and (4) changes in molecular shape and size.
Denaturation can be brought about by the application of physical, chemical and biological methods. Physical methods include heating, freezing, application of surface forces, sound waves, grinding, pressure, and radiation including ultraviolet and ionization radiation. Chemical methods include employing chemical agents such as solvents, pH adjusters, and salts. Biological methods include the use of proteolytic enzymes.
Protein denaturation brought about by heating, usually at 55.degree. to 75.degree. C., conventionally requires the use of a solvent to, inter alia, avoid concomitant decomposition of the polypeptide chain, and to preferably provide a dilute solution to avoid intermolecular interactions of the denatured protein. Aqueous, non-aqueous and aqueous-alcohol solutions have all been used.
A general discussion of proteins including classifications of proteins may be found in John M. deMan, "Principles Of Food Chemistry" 2.sup.nd Edition, Van Nostrand Reinhold, New York, N.Y., (1990) at pages 89 & ff, and Grant & Hackh's Chemical Dictionary, 5.sup.th Edition, McGraw-Hill, Inc., New York, N.Y. (1987) pages 477-478, each of which is incorporated herein by reference.
Chewing gums are traditionally comprised of a water insoluble base portion and a water soluble portion which contains flavors and sweeteners. The base portion includes a gum base part which includes a masticatory substance which imparts the chew characteristics to the final product. The gum base typically defines the release profile of flavors, and sweeteners and plays a significant role in the gum product. The flavors and sweeteners provide the sensory appeal aspects of the chewing gum.
Chewing gum bases conventionally contain materials called elastomers which provide the bounce or rubber character to the gum. Elastomers are water-insoluble polymers, both natural, such as natural rubbers and chicle, and synthetic polymers, such as styrene butadiene copolymers, polyisobutylene, polyethylene and the like. The elastomers are usually combined with polyvinyl acetates (PVAc) of varying molecular weight to provide stretch or elasticity to the gum base. Conventional gums will also contain materials such as resins which are used as elastomer solvents to soften the elastomer; waxes; fats and/or oils which can act as plasticizers; fillers and optionally, antioxidants and emulsifiers.
Conventional ingredients and techniques for the manufacture of chewing gums are known such as described in Sugar Confectionery Manufacture, 2.sup.nd Edition, E. B. Jackson, editor, Blackie Academic & Professional, Glasgow, NZ (1995), at pages 259-286, incorporated herein by reference.
Conventional ingredients and techniques for the manufacture of confectionery compositions such as, for example, nougats are disclosed in "Choice Confections", Walter Richmond, Chapter 14, page 250, Manufacturing Confectionery Publishing Company (1954), incorporated herein by reference.
Native proteins, due to their general lack of flexibility, do not exhibit or mimic properties of gum base or confectionery ingredients such as elasticity, extensibility and chewability. Denatured proteins have been used in chewing gums but the art has not provided protein-based gums on a sensory level with conventional gums. For example, U.S. Pat. No. 5,482,722 discloses a proteinaceous chewable base for use with confectionery products in which prolamine is dissolved in an alcohol/water solvent system and a texturizing agent is added to form a precipitate with the texturizing agent entrapped therein.
While such systems can be used to form proteinaceous materials that can be substituted for elastomers conventionally used in gums and confectionery compositions, such materials still do not effectively convey the same sensory properties that are associated with conventional chewing gums and confectionery products.
It would therefore be a significant advance in the art of developing gums and confectionery products to provide such products with proteinaceous materials as defined herein and to endow such products with the same or similar sensory characteristics as conventional gums and confectionery products.
It would be a further advance in the art to provide proteinaceous materials which have the properties of one or more ingredients of conventional gums and confectionery products such as elastomers, PVAc, waxes and the like, and which can be used in chewing gums and confectionery products as substitutes for one or more conventional ingredients. It would also be desirable to provide chewing gums and confectionery products based on proteinaceous materials which provide the sensation of a traditional gum or confectionery product, which can be eaten like food and digested, and/or which are biodegradable.